The invention relates to a method of forming a wear and scratch resistant protective layer on a surface, and to an object having an at least partly electroconductive support having a surface provided with a protective layer, this surface including at least a first surface area whose protective layer is an electrochemically formed outer layer, and a second surface surface area, the first and second surface areas being distinguishable by virtue of the fact that they differ from each other in at at least one visual property.
Such a method, and such an object, are disclosed in U.S. Pat. No. 3,284,321. In accordance with said patent specification, a surface is partially provided with a mask and subsequently electrochemically treated by anodizing it. Only the first, non-masked area of the surface is provided with an anodized layer. As described in said patent specification, the anodized area of the surface is subsequently sealed, so that it is no longer porous. Next, the mask is removed, for example by means of a solvent, and the surface is re-anodized. As the surface area anodized during the first anodizing treatment is sealed, the second anodizing treatment has little or no effect on the surface area anodized during the first anodizing treatment.
In this manner, a surface is obtained comprising two or more optically different areas, which surface is wear and scratch-resistant, and protected against chemical attack, said surface additionally being-visually attractive. Also the anodized layer formed during the second anodizing treatment is preferably sealed.
As a result of said properties, electrochemically treated surfaces, such as anodized and chrome-plated surfaces can very suitably be used as the outer layer of parts of utensils which are subjected to intensive contact with users, such as housing parts of, in particular shaver heads, of shavers (in this respect, also the resistance to solvents and compositions for personal care such as shaving lotions, shaving soap and the like is important), control buttons, gear lever knobs, handles, clasps of bags and suitcases, and stationery.
However, the removal of the mask and the re-anodizing treatment are laborious. In addition, the use of solvents to remove masks requires special measures to preclude emissions of volatile solvents into the environment and to preclude excessive exposure of employees to such volatile solvents.
It is disclosed in U.S. Pat. No. 3,450,606 to partially anodize and color surfaces by first anodizing the whole surface and, if necessary, coloring it, after which parts of the anodized and, possibly, colored surface are partially masked, whereafter the anodized layer is etched from the non-masked parts and, subsequently, the surface is again immersed in an anodizing bath, whereby the etched parts are anodized in a second color. Also these anodized surfaces can be masked, partially etched and anodized in a different color. Repeatedly anodizing, masking, etching and re-anodizing is laborious and hence expensive.
U.S. Pat. No. 3,284,21 and German patent application 23 63 667 both describe the application of a resist onto the areas of a surface that are not to be anodized, after which the surface is anodized and, next, the resist is removed by immersing in a bath. Also in this case, the removal of the resist after the anodizing treatment is laborious. In addition, the initially masked surface region is not provided with a protective layer.
Japanese patent application 62-278277 describes a similar method of partially anodizing a surface, wherein, in addition, the surface is provided with a transparent protective film which covers the anodized and the non-anodized parts of the surface. The application of such a resist requires an additional operation and generally results in a not entirely satisfactory resistance to attack when an object coated with such a resist is intensively used.